Cigarette smoke and asbestos activate poly-ADP-ribose polymerase in alveolar epithelial cells

Our plain-English summary of Cigarette smoke and asbestos activate poly-ADP-ribose polymerase in alveolar epithelial cells, by D.W. Kamp, M. Srinivasan, S.A. Weitzman (Journal of Investigative Medicine, 2001).

The study

• Authors: D.W. Kamp, M. Srinivasan, S.A. Weitzman
• Journal: Journal of Investigative Medicine
• Published: 2001;49(1):68-76
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Cigarette smoke augments asbestos-induced bronchogenic carcinoma in a synergistic manner by mechanisms that are not established. One important mechanism may involve alveolar epithelial cell (AEC) injury resulting from oxidant-induced DNA damage that subsequently activates poly (ADP-ribose) polymerase (PARP), an enzyme involved in DNA repair that can deplete cellular energy stores. We previously showed that whole aqueous cigarette smoke extracts (CSE) augment amosite asbestos-induced DNA damage and cytotoxicity to cultured AEC in part by generating iron-induced free radicals. We hypothesized that CSE increase asbestos-induced AEC injury by triggering PARP activation resulting from DNA damage caused by iron-induced free radicals.

Methods: Aqueous CSE were prepared fresh on the day of each experiment. PARP activity in WI-26 (a type I-like cell line) and A549 (a type II-like cell line) cells was assessed by the uptake of labeled NAD over 4 hours and confirmed on the basis of the reduction of PARP levels in the presence of a PARP inhibitor, 3-aminobenzamide (3-ABA). Cell survival was assessed by trypan blue dye exclusion.

Results: Hydrogen peroxide (H2O2; 1-250 microM), CSE (0.4-10 vol%), and amosite asbestos (5-250 micrograms/cm2) each caused PARP activation in WI-26 and A549 cells. The combination of asbestos (5 micrograms/cm2) and CSE (0.04-10%) induced WI-26 and A549 cell PARP activation without evidence of synergism. 3-ABA significantly attenuated WI-26 and A549 cell PARP activity and cell death after exposure to H2O2, CSE, and asbestos. Phytic acid, an iron chelator, catalase, and superoxide dismutase each decreased WI-26 cell PARP activation caused by asbestos and CSE.

Conclusions: CSE and asbestos induced PARP activation in cultured AEC in a nonsynergistic manner. These data provide further support that asbestos and cigarette smoke are genotoxic to relevant lung target cells and that iron-induced free radicals in part cause these effects.

In plain English

This laboratory study tested how amosite asbestos and an extract of cigarette smoke affect PARP, an enzyme that responds to DNA damage. It used two lines of human lung cells grown in dishes: WI-26 cells, which resemble alveolar type I cells and come from embryonic lung, and A549 cells, which resemble type II cells and come from a lung cancer. Hydrogen peroxide, smoke extract and amosite each raised PARP activity in both cell lines. WI-26 cells responded at lower doses: smoke extract 1% versus 5%, and asbestos 5 versus 250 micrograms per square centimetre. A PARP blocker, 3-aminobenzamide, reduced this activity. Smoke extract plus asbestos raised PARP activity, but the authors could not detect a synergistic effect in either cell type. The combination mildly reduced WI-26 cell numbers (reported as 20%), and the blocker lessened this. An iron binder (phytic acid), catalase and superoxide dismutase each blocked PARP activation in WI-26 cells. The authors concluded that the two agents activate PARP nonsynergistically, partly through iron-induced free radicals. They said the findings need testing in cells taken directly from lungs.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: in vitro laboratory experiment on cultured human lung cell lines
• Who was studied: Two human cell lines: WI-26 cells (SV-40-transformed, derived from human embryonal lung, alveolar type I-like) and A549 cells (derived from human bronchoalveolar carcinoma, alveolar type II-like); generally at least six separate experiments per group
• Exposure: Amosite asbestos (UICC reference standard), 5 to 250 micrograms per square centimetre; aqueous whole cigarette smoke extract from unfiltered Pall Mall cigarettes, 0.4 to 10% by volume, alone or combined with asbestos (5 micrograms per square centimetre) for 4 hours; hydrogen peroxide for 30 minutes as a comparison. The authors noted that about 0.1% smoke extract is estimated to simulate an adult smoker's lungs, and that 0.01 to 0.1% gave negligible PARP activation in preliminary experiments.
• Main results:
  • Hydrogen peroxide activated PARP in both cell lines, at a lower dose in WI-26 cells than in A549 cells
  • Baseline PARP activity was nearly 2-fold greater in A549 cells than in WI-26 cells
  • Smoke extract activated PARP in both cell lines, starting at 1% in WI-26 cells and at 5% in A549 cells
  • At the highest smoke extract dose (10%), PARP activity rose further and cell numbers fell by 87% (WI-26) and 60% (A549)
  • Amosite asbestos activated PARP in a dose-dependent manner, starting at 5 micrograms per square centimetre in WI-26 cells versus 250 in A549 cells
  • The PARP inhibitor 3-aminobenzamide (2.5 mM) reduced PARP activity caused by hydrogen peroxide, smoke extract and asbestos in both cell types
  • No synergistic interaction between asbestos and smoke extract in activating PARP was detected in either cell type
  • In WI-26 cells, smoke extract (0.6 to 1%) plus asbestos (5 micrograms per square centimetre) mildly reduced cell numbers (reported as 20%), and 3-aminobenzamide attenuated this
  • In A549 cells, 3-aminobenzamide blocked cell death from 10% smoke extract plus asbestos. Mean cell numbers (millions) were 2.55 for controls, 0.96 for smoke extract alone, 1.02 for smoke extract plus asbestos, and 2.48 with 3-aminobenzamide added (n=5).
  • Phytic acid (an iron chelator), catalase and superoxide dismutase each blocked PARP activation in WI-26 cells exposed to 1% smoke extract plus asbestos
  • The authors interpreted the antioxidant results as showing that iron-induced free radicals account in part for PARP activation in WI-26 cells
• The authors' conclusion: The authors concluded that smoke extract and asbestos induce PARP activation in cultured alveolar epithelial cells in a nonsynergistic manner, with iron-induced free radicals partly responsible
• Limitations the authors state:
  • The NAD incorporation assay does not precisely measure polymer levels and can show artificially high PARP activity even in controls
  • The study was not designed to identify the source of the iron
  • The relevance of these cell-culture findings needs further study, ideally in primary isolated lung epithelial cells
  • The role of reactive nitrogen species was not determined

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite.

Medical terms in this study, explained in our Lexicon: Bronchogenic Carcinoma, Amosite, A549 Cells, Superoxide.

Related studies

• Cigarette smoke augments asbestos-induced alveolar epithelial cell injury: role of free radicals — D.W. Kamp, M.J. Greenberger, et al. (1998)
• Modulation of cell and DNA damage by poly(ADP)ribose polymerase in lung cells exposed to H(2)O(2) or asbestos fibres — T. Ollikainen, A. Puhakka, et al. (2000)
• P53 mediates amosite asbestos-induced alveolar epithelial cell mitochondria-regulated apoptosis — V. Panduri, S. Surapureddi, et al. (2006)
• Asbestos exposure affects poly(ADP-ribose) polymerase-1 activity: role in asbestos-induced carcinogenesis — M. Tomasetti, M. Amati, et al. (2011)
• Asbestos causes apoptosis in alveolar epithelial cells: role of iron-induced free radicals — A. Aljandali, H. Pollack, et al. (2001)
• Crocidolite activates NF-kappa B and MIP-2 gene expression in rat alveolar epithelial cells. Role of mitochondrial-derived oxidants — K.E. Driscoll, J.M. Carter, et al. (1998)

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